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Newly-assembled B-Robot won't stand - motors whining
04-20-2020, 09:04 AM
Post: #1
Newly-assembled B-Robot won't stand - motors whining
I have just finished assembling my B-Robot (plastic components printed by myself, motors, electronics and everything else from JJRobots).

I lay it down, switch on and the arm wiggles, as expected. The robot then moves a few centimetres to one side and the motors start whining loudly. It will not stand upright, apart from one single time this morning when it did stand perfectly well - I couldn't connect with my phone so I turned the robot off and back on shortly after - and then I was back to the whining motors.
  • The batteries are new.
  • I have adjusted the drivers - the only effect of adjusting the driver pots is to vary the volume of the whining!
  • I have reloaded the firmware.
  • The motor cables are plugged in correctly - M2 to the motor under the servo, M1 to the other one.

Now I'm stuck and seeking guidance...

David
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04-20-2020, 11:33 AM (This post was last modified: 04-20-2020 11:38 AM by JJrobots JP.)
Post: #2
RE: Newly-assembled B-Robot won't stand - motors whining
Hi David, in order to narrow down the problem, could you:
1) try with different batteries (it looks like it is lacking of power to spin the wheels as it should)
2) Unplug one stepper motor driver and start-up the robot and see if it still make the noise.
3) Could you please upload a photo of you set-up? How the DEVIA control board has been attached to the plastic part and so on. If the robot was capable of balancing itself correctly, the motor cables should be fine.
4) Could you try to debug the robot connecting it to your computer and listening the messages sent via the SERIAL MONITOR? more info at the very end of this page: https://www.jjrobots.com/b-robot-evo-2-a...uide-v1-2/ (DEBUG MODE)
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04-20-2020, 01:01 PM
Post: #3
RE: Newly-assembled B-Robot won't stand - motors whining
OK - tried more batteries from the same batch, same result. Tried 6 batteries from another batch - and the robot stood up. Wink Maybe the first lot wasn't a good pack of batteries...

One problem I could see was that the battery monitor on the phone went into the yellow a very short time after switching on. I think my robot is hitting the batteries very hard. Any suggestions on how I can make them last a bit longer? Maybe the Vref on the drivers is too high - what Vref value do you recommend?

You mention LiPo batteries briefly on your website. I do have a small 3S 1000mAh 20C-rated LiPo battery - would that work? It is physically small enough to fit into the battery box space, and I see no problem in printing a little box for it and its battery monitor. Before you say anything - I have a lot of experience with LiPo batteries, although I don't like them very much.

Thanks,
David

BTW: In the process of faffing about I managed to pop on of my motor drivers (plugged the motor in when I thought the power was off - it wasn't Sad ). Fortunately I had a spare of the same type to replace it. Nobody's fault but mine... I should have checked more carefully.
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04-20-2020, 08:24 PM (This post was last modified: 04-20-2020 08:25 PM by JJrobots JP.)
Post: #4
RE: Newly-assembled B-Robot won't stand - motors whining
(04-20-2020 01:01 PM)David_J Wrote:  OK - tried more batteries from the same batch, same result. Tried 6 batteries from another batch - and the robot stood up. Wink Maybe the first lot wasn't a good pack of batteries...

One problem I could see was that the battery monitor on the phone went into the yellow a very short time after switching on. I think my robot is hitting the batteries very hard. Any suggestions on how I can make them last a bit longer? Maybe the Vref on the drivers is too high - what Vref value do you recommend?

You mention LiPo batteries briefly on your website. I do have a small 3S 1000mAh 20C-rated LiPo battery - would that work? It is physically small enough to fit into the battery box space, and I see no problem in printing a little box for it and its battery monitor. Before you say anything - I have a lot of experience with LiPo batteries, although I don't like them very much.

Thanks,
David

BTW: In the process of faffing about I managed to pop on of my motor drivers (plugged the motor in when I thought the power was off - it wasn't Sad ). Fortunately I had a spare of the same type to replace it. Nobody's fault but mine... I should have checked more carefully.
Good!
It is quite easy to get bad quality batteries nowadays. They are everywhere. I trick someone showed me time ago was this: https://youtu.be/ZywsCbWEun8?t=2 or this one: https://www.youtube.com/watch?v=V8Hro4Ud7-I Depending on the density of its electrolyte you may know how good it is.

Regarding the Vref: Between 0.96v and 0.70v should be fine ;-)

That Lipo will work nicely! those 11.1V and that 20C will make the motors to get about a 20% more torque (and yes, use the battery monitor)

Glad to read you found the problem :-D
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04-25-2020, 01:15 PM
Post: #5
RE: Newly-assembled B-Robot won't stand - motors whining
Late update:

I found a 2300mAh LiFe battery in my storage box (3 of A123 cells) - wired it up and it all works very well! I had to make a couple of extension pieces to raise the side plates up from the motors about 10 - 12 mm, and a box to keep the battery secure.

The battery pack is quite heavy and that, together with the slightly increased height, means that the robot wobbles a bit when standing still (it didn't when I used the AA batteries). I will have to study PID tuning again (it's been a while).
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04-27-2020, 01:31 PM
Post: #6
RE: Newly-assembled B-Robot won't stand - motors whining
(04-25-2020 01:15 PM)David_J Wrote:  Late update:

I found a 2300mAh LiFe battery in my storage box (3 of A123 cells) - wired it up and it all works very well! I had to make a couple of extension pieces to raise the side plates up from the motors about 10 - 12 mm, and a box to keep the battery secure.

The battery pack is quite heavy and that, together with the slightly increased height, means that the robot wobbles a bit when standing still (it didn't when I used the AA batteries). I will have to study PID tuning again (it's been a while).

Upload a photo or never happened!
Do you think the motors have more torque with the LIPO?
try adjusting the PID values directly from the control APP, it will give you a good idea about which VALUES set performs better.
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04-28-2020, 11:21 AM (This post was last modified: 04-28-2020 11:22 AM by David_J.)
Post: #7
RE: Newly-assembled B-Robot won't stand - motors whining
(04-27-2020 01:31 PM)JJrobots JP Wrote:  Upload a photo or never happened!
Do you think the motors have more torque with the LIPO?
try adjusting the PID values directly from the control APP, it will give you a good idea about which VALUES set performs better.

Video here!
It also shows the wobble I need to sort out... I know it's on carpet, but it's the same on a hard smooth surface.
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05-01-2020, 05:40 PM
Post: #8
RE: Newly-assembled B-Robot won't stand - motors whining
could be the connector wiring on the motor to the board? I'm having the same Issue, If I follow the wiring schematic I have black, green, blue and red. SB black, green, red and blue.does it change something?
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05-05-2020, 07:02 AM
Post: #9
RE: Newly-assembled B-Robot won't stand - motors whining
(05-01-2020 05:40 PM)gafil001 Wrote:  could be the connector wiring on the motor to the board? I'm having the same Issue, If I follow the wiring schematic I have black, green, blue and red. SB black, green, red and blue.does it change something?

I don't think it's a motor wiring issue - it's fine when it's moving along now, although it over-corrects when standing still. Fixing that is the current work in progress, although not so urgent.

The 'falling over and whining' issue was solely to do with the batteries not being able to supply enough power - now fixed.
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